Fort Detrick Maryland is home to the US Army's Institute of Infectious Diseases.

Scientists here are developing defences to the world's most biological agents, but now there is an alarming question.

Could someone here have turned his knowledge against the United States?

Security flawed

Dr Richard Crosland worked at Fort Detrick for 11 years. He told the BBC that security there is deeply flawed. Stocks of lethal bacteria, like anthrax, were not monitored, he said.

Mr Crosland said that he could easily have walked away from Fort Detrick with biological agents

"No one came in ever and said: 'Where is this material? Where is this stored? What have you done with it?'" He addded that it would have been easy for him to take dangerous biological agents.

"You could have taken anything out," he said. When he left for three days, he walked past security with boxes full of his personal belongings.

Not once was he stopped and asked what the boxes contained.

Anthrax expert under suspicion

Years of lax security at Fort Detrick may have cost America dearly.

Investigators are increasingly convinced that the anthrax attacks were the work of an insider, a scientist, who for a time at least, may have had access to top-secret bio-defence research.

It is five months since the first anthrax attacks. The FBI is using DNA tests to see which lab the weaponised anthrax came from.

Five people died in the anthrax attacks last autumn

But one senior molecular biologist thinks investigators already have a clear idea of the culprit.

"He's an anthrax expert who has had the anthrax vaccine up to date, which means that he has had a yearly booster," said Barbara Hatch Rosenberg, director of the Federation of American Scientists' Chemical and Biological Weapons Programme.

She believes that the culprit has worked in that past at the Army's research laboratory for infectious diseases at Fort Detrick and probably works for a private contractor now in bio-defence programme.

Awkward subject

White House spokesman Ari Fleischer said, "I wish it were that easy and that simple right now."

He said the FBI is still investigating several suspects. "It's not as if there is only one," Mr Fleischer said.

For the US Government, the anthrax investigation is fast becoming an awkward subject. The Fort Detrick lab remains a focus of FBI interest.

But everyone seems to agree the anthrax attacks were domestic terrorism made possible by a serious breakdown in security.